1. Field of the Invention
This invention relates to a specific optically active compound. More particularly, it relates to an optically active bisaryl compound.
2. Description of the Prior Art
Liquid crystals have been employed in various electrooptical devices. Recently they have been applied to display devices of, for example, watches, electric calculaters and automobile panels. Most of the liquid crystal display devices which are practically employed today are those prepared by taking advantage of the dielectric alignment effects of twistnematic liquid crystals or cholesteric liquid crystals. Recently it has been often attempted to develop liquid crystal display systems other than those described above. Examples of these new systems include STN systems and cholesteric/nematic phase transition systems.
Each liquid crystal composition to be used in such a liquid crystal display device as described above is adjusted in such a manner as to achieve the aimed helical pitch by introducing an optically active group into nematic liquid crystals or by adding an optically active substance thereto. For example, there is known a Shiff base liquid crystal obtained from p-alkoxybenzaldehyde and (+)-p-amino-2-methylbutylbenzene. An example of the optically active substance to be added is 4-(2-methylbutyloxy)-4'-cyanobiphenyl. However it is necessary to use a disadvantageously large amount of this compound in order to achieve the aimed properties, since it has a long twist pitch of cholesteric liquid crystals.